Conventional depth adjusting devices of nail guns are generally installed inside the safety devices, for example, U.S. Pat. No. 6,170,729, U.S. Pat. No. 6,427,896 and US 2003/0019901 disclose that the adjusting devices and the safety devices are disposed on the outside of the barrels. The addition of other adjusting devices makes the whole structures more complicated and limited in stabilization. Besides, it is more inconvenient to make adjustment because of its vicinity to the muzzle of the barrel.
Such structure has shortcomings, such as unstable structure, inconvenience for use and complicated manufacture. Because the safety device is assembled by pieces, an adjustment assembly is additionally attached in the middle thereof, which will cause the safety device to shake while the adjustment assembly acts, so as to make the structure unstable and unable to locate precisely. Besides, the adjustment assembly is near the muzzle, it is unable to make an adjustment by one hand that presses the trigger while use. If it needs to adjust the depth of nailing frequently, which is inconvenient for use. Moreover, the connection between the adjustment assembly, the safety device and the trigger uses corresponding connection structure, it needs to design the corresponding connection structure individually for application of different safety devices and triggers, which is complicate to manufacture.
As for the shortcomings mentioned above, the inventor has a TW Appl. No. 93133904 adjustable safety device approved, which discloses that a main body of a nail gun is equipped with an adjusting assembly and a moving assembly between a trigger and a magazine. One end of an acting piece of the adjusting assembly is connected with the trigger. The acting piece is connected with a supporting piece, and the acting piece and one end of the supporting piece are coupled with a moving piece of the moving assembly. Meanwhile, the moving piece is connected with one end of an interlocking assembly of a safety device via a compressing piece. When adjusting the supporting piece, the distance between the acting piece and the moving piece can be controlled precisely, so as to precisely adjust the depth between the actuation point of the safety device and the muzzle. However this case does not consider that the nail gun is still dry firing while the nail is insufficient, which causes the damage of the structure of the nail gun and the firing device.